CN108024849B

CN108024849B - Cryopreservation of ungulate embryos

Info

Publication number: CN108024849B
Application number: CN201680052779.9A
Authority: CN
Inventors: B·V·桑切斯
Original assignee: Genus PLC
Current assignee: ABS Global Inc
Priority date: 2015-07-14
Filing date: 2016-07-13
Publication date: 2021-03-05
Anticipated expiration: 2036-07-13
Also published as: EP3322379A2; JP2018529374A; RU2018101430A3; EP3322379B1; MX2018000460A; US11793193B2; WO2017009713A3; US20220183276A1; RU2018101430A; BR102016003292B1; CA2992414A1; US20230404069A1; US20180352808A1; BR102016003292A2; RU2730597C2; CN112961824A; WO2017009713A2; US11297831B2; CO2018001233A2; CN108024849A

Abstract

Techniques for cryopreserving ungulate embryos for transplantation into recipient females are described.

Description

Cryopreservation of ungulate embryos

Cross-referencing

This application claims priority to U.S. provisional application serial No. 62/192,544 filed on 7, month 14, 2015, the disclosure of which is incorporated herein by reference in its entirety.

Background

In vitro embryo production is a major component of bovine breeding. More embryos are typically produced than are implanted. Although in vitro Embryo Transfer (ET) of vitrified embryo production (IVP) a conception rate of more than 30% has recently been achieved, the complex process of recovery of these embryos after vitrification remains an obstacle to the commercial application of this technique. Cryopreservation of bovine embryos requires new and efficient protocols.

Disclosure of Invention

The present invention provides techniques for cryopreserving bovine embryos and/or using cryopreserved bovine embryos to effect fertilization. The invention also provides, inter alia, cryopreserved embryos, populations of such cryopreserved embryos, and systems for producing and/or storing them.

In addition, the present invention also includes certain available techniques for embryo transfer of cryopreserved embryos, particularly for identification of sources of problems for resuscitating (e.g., thawing, implantation, etc.) cryopreserved embryos. For example, the present invention recognizes that the personnel and time required to resuscitate viable cryopreserved embryos according to many standard techniques raise concerns regarding their commercial applicability.

Furthermore, the present disclosure also recognizes that there is a need for techniques for transplantation of cryopreserved embryos that achieve improved conception rates relative to most standard techniques using cryopreserved embryos, it being understood that such standard techniques typically achieve lower conception rates than achieved using fresh embryos. In addition, the present disclosure provides techniques to achieve a desired (e.g., about 10% or more) conception rate of cryopreserved embryos.

In some embodiments, the present invention provides methods comprising the steps of, for example: obtaining an In Vitro Produced (IVP) ungulate embryo; freezing and preserving the embryo; and transferring the embryo into a recipient ungulate for cryopreservation and transfer to achieve a pregnancy rate of at least about 10%.

In some embodiments, obtaining one or more in vitro produced embryos comprises the steps of, for example: recovering one or more oocytes from the female; maturing one or more oocytes in vitro; fertilizing one or more mature oocytes with semen or one or more detached sperm cells, thereby producing one or more fertilized eggs; and denuding and incubating one or more fertilized eggs. In some embodiments, semen is used that is gender separated. In some embodiments, the semen is not gender separated.

In some embodiments, the in vitro matured oocytes include, for example: incubating the oocyte in a physiologically relevant range of at least one condition selected from the group consisting of temperature, presence or amount of gas, humidity, pH, osmolality and combinations thereof. In some embodiments, the presence or amount of gas is selected from the group consisting of O₂And CO₂Group (d) of (a). In some embodiments, the step of maturing the oocyte in vitro comprises: at 35-40 deg.C, 3-9% CO₂And incubating the oocytes at saturated humidity. In some embodiments, the step of denuding and incubating the fertilized egg comprises 5% CO at 35-40 deg.C₂And incubating the fertilized egg under saturated humidity. In some embodiments, the step of denuding and incubating the fertilized egg further comprises incubating the fertilized egg at 5% O₂And (5) incubating the fertilized eggs.

In some embodiments, cryopreservation of embryos comprises the following steps, for example: incubating the embryo in a solution comprising a cryoprotectant; and the embryos immersed in liquid nitrogen. In some embodiments, the step of cryopreserving the embryo comprises the steps of: incubating the embryo in a freezing solution consisting of 1.0-4M ethylene glycol at a first temperature in the range of about 10 ℃ to about 38 ℃ for 5-30 minutes; loading the embryos into a container, wherein the gas bubbles separate the embryos from the thawing solution comprising ethylene glycol in a osmotic dilution medium; exposing the embryo to a temperature in the range of about-2 to about-10 ℃ for a time period in the range of about 1 minute to about 60 minutes; cooling at a rate in the range of about-0.2 to about-0.8 ℃ per minute until a second temperature in the range of about-30 to about-36 ℃ is reached; and the embryos were stored by immersion in liquid nitrogen. In some embodiments, the ethylene glycol is present at a final concentration in the range of about 0.2 to about 1.3 molar.

In some embodiments, embryos are cryopreserved for direct transfer into recipient females.

In some embodiments, transferring the embryo comprises the steps of: incubating the embryos in medium supplemented with Bovine Serum Albumin (BSA) under mineral oil for a period of time ranging from about 5 to about 9 days; and transferring the embryo into a recipient ungulate. In some embodiments, the medium is selected from the group consisting of C4 medium, SOF medium, SOFaa medium, and combinations thereof. In some embodiments, the medium is supplemented with one or more of serum, fetal bovine serum, bovine serum albumin, and/or one or more amino acids.

In some embodiments, the transferred embryo is at a developmental stage selected from the group consisting of morula, early blastocyst, and expanded blastocyst.

In some embodiments, the subject is a syngeneic recipient ungulate. In some embodiments, the recipient ungulate is in natural estrus. In some embodiments, the embryo is fresh, vitrified, or frozen. In some embodiments, the ungulate is a bovine. In some embodiments, the species of embryo is selected from the group consisting of bovine sire, buffalo, and a cross of bovine sire and buffalo.

In some embodiments, the invention provides cryopreserved embryos produced by a method comprising the steps of, for example: obtaining an In Vitro Produced (IVP) ungulate embryo; cryopreserving the embryo under conditions such that when the cryopreserved embryo is transferred to a recipient ungulate, a pregnancy rate of at least about 10% is achieved. In some embodiments, obtaining embryos produced in vitro comprises the steps of, for example: recovering the oocyte from the female; maturing oocytes in vitro; fertilizing the mature oocyte with semen; denuding and incubating the fertilized egg. In some embodiments, maturing the oocyte in vitro comprises incubating the oocyte in at least one physiologically relevant range of conditions selected from the group consisting of temperature, presence or amount of gas, humidity, pH, osmolality, and combinations thereof. In some embodiments, transferring the embryo comprises the steps of: incubating the embryos in medium supplemented with Bovine Serum Albumin (BSA) under mineral oil for a period of time ranging from about 5 to about 9 days; and transferring the embryo into a recipient ungulate.

In some embodiments, the medium used according to the invention is or comprises a medium selected from the group consisting of C4 medium, SOF medium, SOFaa medium, and combinations thereof. In some embodiments, the medium is supplemented with one or more of serum, fetal bovine serum, bovine serum albumin, and/or one or more amino acids.

In some embodiments, embryos cryopreserved and/or transplanted according to the present invention are at a developmental stage selected from the group consisting of morula, early blastocyst, and expanded blastocyst.

In some embodiments, the present invention provides an apparatus comprising: a container; cryopreserved embryos in a cryoprotectant solution located within a first region of the container, the first region flanked by: a second zone and a third zone, each zone containing air, the sides of the second zone and the third zone being: a fourth zone and a fifth zone, each zone containing a thawing solution, the fourth zone and the fifth zone flanked by: a sixth zone and a seventh zone, each zone containing air, the sixth zone and the seventh zone being flanked by an eighth zone and a ninth zone, each zone containing a thawing solution. In some embodiments, one or more of the zones is a chamber, wherein the chamber is defined by a physical separation entity that provides a barrier between it and at least one other zone adjacent to it. In some embodiments, the present invention provides a plurality of devices.

In some embodiments, the present invention provides a method comprising the steps of: cryopreserving a plurality of ungulate embryos; and transferring the plurality of embryos to a recipient ungulate, wherein cryopreservation and transfer is performed such that a conception rate of at least 30% is achieved. In some embodiments, the step of cryopreserving each embryo in the cryopreservation solution comprises: positioning an embryo in a first region of a container, the first region flanked by: a second zone and a third zone, each zone containing air, the second and third zones being flanked by: a fourth zone and a fifth zone, each zone containing a thawing solution, the fourth zone and the fifth zone flanked by: a sixth zone and a seventh zone, each zone containing air, the sixth zone and the seventh zone being flanked by: an eighth zone and a ninth zone, each zone containing a thawing solution.

In some embodiments, the invention provides methods of freezing embryos, for example, comprising: exposing ungulate embryos to a freezing Solution (SC) consisting of about 1 to about 4M ethylene glycol at 35 ℃ for 10 minutes; placing each embryo into a freezing Solution (SC) in a straw-sized container such that the embryos in the freezing solution are surrounded by four columns of thawing Solution (SD) and interspersed between them by air columns, wherein the thawing solution comprises about 0.75M ethylene glycol; exposing the container to temperature conditions stable at a temperature in the range of about 0 ℃ to about-10 ℃; placing in a freezer for two minutes and then crystallizing columns above and below the embryos; holding the embryo at a temperature in the range of about 0 ℃ to about-10 ℃ for 1 to 60 minutes; cooling at a rate of about-0.2 ℃ to about 0.8 ℃ per minute until a second temperature in the range of about-30 ℃ to about-36 ℃ is reached; and the frozen embryos were immersed in liquid nitrogen. In some embodiments, the container containing the frozen embryo is immersed in liquid nitrogen after reaching a second temperature in the range of about-30 ℃ to about-36 ℃.

In some embodiments, the invention provides methods of thawing embryos, for example, comprising: exposing a container containing a cryopreserved embryo in a cryopreservation solution in a first region of the container flanked by: a second zone and a third zone, each zone containing air, the sides of the second zone and the third zone being: a fourth zone and a fifth zone, each zone containing a thawing solution, the fourth zone and the fifth zone flanked by: a sixth zone and a seventh zone, each zone containing air, the sixth zone flanked by the seventh zone: an eighth zone and a ninth zone, each zone containing a thawing solution to contain room temperature air for a first period of time sufficient to begin thawing frozen embryos; exposing the container to a thawing environment characterized by a thawing temperature in the range of about 10 ℃ to about 38 ℃ for a second period of time sufficient to thaw the frozen solution; and mixing the thawing solution, the freezing solution and the embryo in a container. In some embodiments, the first period of time is in the range of about 10 ℃ to about 38 ℃. In some embodiments, the second period of time is in the range of about 20 ℃ to about 38 ℃. In some embodiments, the thawing environment is or comprises a liquid bath. In some embodiments, the thawing temperature is in the range of about 10 ℃ to about 38 ℃. In some embodiments, the mixing step is accomplished by gently stirring the vessel. In some embodiments, the thawing method further comprises the step of transferring the embryo into a recipient ungulate. In some embodiments, the implanting is performed simultaneously with or after the exposing step or the mixing step. In some embodiments, the step of transferring comprises transferring the embryo to the uterine horn of the recipient ungulate.

Drawings

FIG. 1 depicts a loading scheme using frozen embryos in embryo direct transfer. As shown in this figure, embryos in frozen solution may be arranged in devices with regions of solution separated by regions of air (e.g., one embryo per device). For example, as shown in FIG. 1, embryos 100 in a freezing solution 200 are located in a first region 300 (grey in FIG. 1) of a column device 400 (e.g., a pipette). Immediately to the side of the first zone are two zones containing air (second zone 305 and third zone 315, each of which is stippled in fig. 1), followed by two zones containing the thawing solution (fourth zone 310 and fifth zone 320, each of which is stippled in fig. 1), followed by two additional zones containing air (sixth zone 325 and seventh zone 335, each of which is stippled in fig. 1), followed by two more zones containing the thawing solution (eighth zone 330 and ninth zone 340, each of which is stippled in fig. 1). The particular device depicted in FIG. 1 is a 0.25mL pipette placed on the center post; the freezing solution was 1.5M ethylene glycol; and the thawing solution was a frozen solution in DPBS 1: 1 dilution to 0.75M ethylene glycol in DPBS.

Fig. 2A and B (both including fig. 2) depict an overview of the freezing (fig. 2A) and thawing (fig. 2B) protocols as outlined in an example of the invention.

Definition of

In order that the invention may be more readily understood, certain terms are defined below. Those skilled in the art will recognize that the definitions of certain terms may be provided elsewhere in the specification and/or will be clear from the context.

About: as used herein, the term "about" or "approximately" for one or more values of interest refers to a value that is close to the referenced value. In certain embodiments, the term "about" or "about" means falling within a range of 25%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less, in any one direction of the referenced value (or greater or less) unless otherwise stated or otherwise apparent from the context (unless the number exceeds 100% of a possible value).

Artificial Insemination (AI): as used herein, the term "Artificial Insemination (AI)" refers to the introduction of semen into the uterus of female cattle by a human hand to achieve pregnancy. In many embodiments, AI is used for breeding, for example, such that the resulting pregnancy is (or is prepared for) brought to parturition. In some embodiments, AI is performed with collected semen. In some embodiments, AI is performed with extracted semen. In some embodiments, AI is performed with semen that has been processed; for example, in some embodiments, semen is already of a sex such that it is enriched in sperm of only one sex. Those skilled in the art will recognize. Unless otherwise specifically indicated, the term "AI" does not include embryo transfer procedures in which, for example, semen may be introduced into a cow to produce an embryo for transfer.

And (3) blastula: as used herein, the term "blastocyst" refers to a structure formed during early development in a mammal. It has an Inner Cell Mass (ICM) that subsequently forms an embryo. The trophoblast is the outer layer of the blastocyst cell. This layer surrounds the inner cell mass (which is the source of embryonic stem cells) and a fluid-filled cavity known as the blastocoel. The trophoblasts produce the placenta. The use of blastocysts for In Vitro Fertilization (IVF) involves incubating fertilized eggs prior to implantation into the uterus of cattle.

Variety: as used herein, the term "breed" refers to a group of ungulates (e.g., cattle) that have a common ancestor and/or have certain distinguishable traits that are not shared with ungulates of other breeds. Those skilled in the art are familiar with species criteria and/or characteristics. In many embodiments, a particular breed is produced and/or maintained by cross-breeding a particular identified parent or parents (e.g., a particular male animal with a particular female animal or with any one of a particular strain of female animals).

Comparative: the term "comparable" is used herein to describe two (or more) groups of conditions, environments, individuals or populations that are sufficiently similar to one another to allow comparison of the results obtained or observed phenomena. In some embodiments, a control group of conditions, environments, individuals, or populations has characteristics that are substantially the same characteristic and one or a small number of varying characteristics. One of ordinary skill in the art will appreciate that when features are substantially the same with sufficient numbers and types, the set of contexts, individuals, or populations are comparable to ensure that a reasonable conclusion is reached that the results or observed phenomena obtained or observed in or using different environments, individuals, or populations are attributable to or indicative of changes in those features. Those skilled in the art will appreciate that the relevant language (e.g., enhance, activate, decrease, inhibit, etc.) used herein will generally refer to comparisons made under comparable conditions.

And (3) hybridization: as used herein, the term "cross" refers to an ungulate (e.g., a cow) produced from gametes of a different breed or species of ungulate (e.g., a cow). Crossbreeding is often performed in dairy cattle farming to produce healthier, higher yielding cattle than parental varieties. Crosses are the artificial breeding of animals from different breeds or strains; in many embodiments, hybrid propagation is designed to take advantage of heterosis (heterosis) to obtain characteristics like yield, fertility and longevity. In some embodiments, this summary includes the following recognition: recent advances in artificial insemination and/or in vitro fertilization can be utilized and are not generally adopted in the dairy industry as may be used to enable and or provide particular advantages with respect to producing and/or maintaining dairy hybrids as described herein. As described herein, particularly interesting cross ungulates are hybrids in which 50% of the somatic chromosomes are from one breed or line and 50% are from a different breed or line (i.e., formed by crossing F0 with individuals from first and second breeds/lines that are distinct from one another, although those of ordinary skill in the art will appreciate that the term "cross" may be used in some embodiments (as will be clear from the context) to refer to any individual whose genome is the result of the cross, rather than 100% being derived from any single breed.

And (3) development stage: as used herein, the term "developmental stage" refers to a stage of embryonic development. In some embodiments, the developmental stages comprise: morula, early blastocyst, and expanded blastocyst.

Direct transplantation: as used herein, the term "direct transfer" refers to a method of slow cryopreservation of embryos. Embryos are incubated in a freezing solution containing a cryoprotectant (e.g., ethylene glycol or glycerol) and exposed to progressively lower temperatures until the embryos are frozen and then submerged in liquid nitrogen. In some embodiments, embryos in a freezing solution are loaded onto a pipette that is exposed to the freezing temperature. The direct transplant method of cryopreservation is also known as slow freezing.

Embryo: as used herein, the term "embryo" refers to a fertilized egg (egg) prepared or stored for eventual implantation into a female ungulate for immediate implantation into the female ungulate.

Fresh transplantation: as used herein, the term "fresh transplant" is used to refer to a method of implanting an embryo into a recipient ungulate (e.g., a bovine) after fertilization-avoiding cryopreservation. In some embodiments, the embryo is incubated in vitro for several days before implantation into a recipient female.

Gamete: as used herein, the term "gamete" is used to refer to a germ cell (e.g., sperm or oocyte) having a haploid chromosome number, particularly a mature sperm or egg capable of fusing with a heterogamete to produce a fertilized egg. Gametes are produced by the process of meiosis.

Sex separated semen: as used herein, the term "sex-separated semen" refers to semen that has been manipulated to select for spermatocytes of only one preferred sex. In some embodiments, sex-separated semen is also referred to as sex-controlled semen. In some embodiments, sex-separated semen is "sex-enriched semen," meaning that the semen has been manipulated to enrich for spermatocytes of only one preferred sex. In some embodiments, sex-enriched semen comprises at least about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 91%, about 92%, 93%, about 94%, about 95%, about 96%, about 97%, about 98%, or about 99% spermatocytes of only one preferred sex.

Genome profiling: as used herein, the term "genomic profile" refers to a representative subset of the total information contained within a genome. Typically, the genomic profile contains genotypes at a particular set of polymorphic loci. In some embodiments, a genomic profile may be associated with a particular characteristic, trait, or set of characteristics thereof, for example, of a particular animal, strain, breed, or hybrid population.

Genotype: as used herein, the term "genotype" refers to a diploid combination of alleles of a given genetic locus or set of related loci in a given cell or organism. Pure zygotes carry two copies of the same allele, and heterozygotes carry two different alleles. In the simplest case of a locus with two alleles "a" and "a", three genotypes can be formed: A/A, A/a and a/a.

Genotyping: as used herein, the term "genotyping" refers to experimental, computational, or observation protocols used to differentiate an individual's genotype at one or more well-defined loci. Those skilled in the art will recognize a variety of techniques that can usefully and efficiently perform genotyping. In some embodiments, genotyping involves direct detection of a nucleic acid or nucleic acid sequence. In some embodiments, genotyping involves indirect detection of a nucleic acid or nucleic acid sequence, e.g., by detecting or analyzing surrogate markers or events that correlate with the presence of a nucleic acid or nucleic acid sequence.

Haploid cells: as used herein, the term "haploid cell" refers to a cell with chromosomes having a single set (1n) of chromosomes-half the number of somatic cells.

Young cows: as used herein, the term "young cow" refers to a female cow that has not yet produced any calves.

And (3) hybridization: as used herein, the term "cross" refers to an ungulate (e.g., a cow) produced as a result of crossing male and female gametes from different breeds or lines of ungulates. Thus, 50% of the autosomal genome (e.g., somatic genome) of a hybrid is typically from a first variety/strain and 50% from a second variety/strain. Of particular interest, as described herein, are hybrids in which 50% of the somatic chromosomes are from the first variety and 50% are from the second variety.

In Vitro Fertilization (IVF): as used herein, the term "in vitro fertilization" refers to a process of fertilizing an egg in vitro using sperm in a living animal. IVF is a process of in vitro fertilization by sperm (i.e., in vitro, literally translated as "in the glass," but understood in the art to mean, for example, in a laboratory or other artificial device). In some embodiments, IVF procedures may involve monitoring and/or stimulating the ovulation process of a female, removing one or more oocytes or oocyte(s) from the female ovary, and/or contacting sperm and oocytes with each other (e.g., in a fluid medium) in a laboratory to achieve fertilization. In some embodiments, IVF involves incubating fertilized eggs (zygotes) in a growth medium and/or implanting them into the female uterus or storing them for future analysis and/or transplantation. In some embodiments, IVF may involve sorting fertilized eggs for a particular desired attribute (e.g., gender).

Strain: as used herein, the term "line" refers to a series of offspring cattle from a common ancestor parent that are developed and maintained by selective breeding.

Seed preparation: as used herein, the term "gametophyte" refers to the process of forming an embryo, typically from two opposite gametes. In some embodiments, the mating involves natural mating. In some embodiments, mating involves artificial insemination. In some embodiments, the mating involves IVF. In many of the embodiments described herein, hybrid progeny is produced using breeding. In many embodiments, hybridization progeny are generated using breeding.

Morula: as used herein, the term "morula" refers to the stage of embryonic development. Morulae are early embryos composed of a cell sphere (called a blastomere) contained within a zona pellucida that are produced by a series of divisions. The morula produces blastocysts by cell differentiation and cavitation. Once the fluid-filled cavity begins to open in the morula, the blastocyst stage of embryonic development begins. During blastocyst formation, morula cells differentiate into an inner cell mass that grows inside the blastocyst cavity and into trophoblast cells that grow outside.

Natural mating: as used herein, the term "natural mating" refers to traditional breeding of cattle that pair males and females without artificial insemination or IVF-based techniques.

A container: as used herein, the term "container" refers to a device for holding one or more cryopreserved embryos. The container may comprise a series of zones or chambers for containing: air, thawing solution, or cryopreservation of embryos in solution. In some embodiments, the container is or includes a straw.

Essentially: as used herein, the term "substantially" refers to a qualitative condition that exhibits an overall or near overall degree or degree of a characteristic or feature of interest. One of ordinary skill in the biological arts will appreciate that biological and chemical phenomena are less likely to complete and/or continue to complete or achieve or avoid absolute results. Thus, the term "substantially" is used to capture the potentially lacking integrity inherent to many biological and chemical phenomena.

The characteristics are as follows: as used herein, the term "trait" refers to a detectable attribute of an individual. Typically, expression of a particular trait may be affected, in whole or in part, by the genetic composition of the individual. In some embodiments, a trait is a characteristic of a particular individual, line, breed or hybrid, for example, which may be relied upon (either alone or as part of a group) to distinguish the individual, line, breed or hybrid.

Ungulates: as used herein, the term "ungulate" refers to a wide variety of large mammals including horses, cattle/cows, pigs, goats, buffalos, sheep, giraffes, camels, deer and hippopotamus. Most terrestrial ungulates use their toes, usually hooves, to support their entire body weight when moving. In some embodiments, the term generally refers to "hoofed" or "ungulates".

Vitrification: as used herein, the term "vitrification" refers to a process of cryopreservation of eggs (oocytes) and embryos. In some embodiments, embryos are exposed to an equilibration and vitrification solution containing a cryoprotectant (e.g., ethylene glycol or glycerol) and submerged in liquid nitrogen as part of a cryopreservation process.

Fertilized egg: as used herein, the term "zygote" refers to a cell that is formed when two gametic cells are combined by sexual reproduction. This is the earliest stage of embryonic development. The zygote is formed by the association of two gametes, representing the first stage of development of a unique organism. Fertilized eggs are produced by fertilization between two haploid cells, an egg (female gamete) and a sperm cell (male gamete), which combine to form a single diploid cell.

Detailed Description

The present invention is based in part on the following findings: with respect to most standard techniques, it is possible to cryopreserve ungulate embryos with an increased conception rate, which is much lower than that achieved with fresh embryos.

In some embodiments, the present invention provides a method comprising the steps of: obtaining an in vitro produced embryo; freezing and preserving the embryo; and transferring the embryo into a recipient ungulate for cryopreservation and transfer to achieve a pregnancy rate of at least about 10%. In some embodiments, the invention provides embryos cryopreserved by the disclosed methods. In some embodiments, the present invention provides containers for freezing, storing, and thawing cryopreserved embryos.

In vitro produced embryos

The use of in vitro produced embryos (IVP) has increased greatly over the last decade (Hasler, 2014). This growth occurs mainly in brazil. In 2013, more than 393,000IVP embryos were transferred to recipients, of which 78% were produced in south America. In the same year, only 8.9% of IVP embryos were frozen from the total number of transplants; for in vivo embryos, this ratio is 59% (Perry, 2013).

IVP embryos are less resistant to cryopreservation than in vivo embryos and Fetal Bovine Serum (FBS) added to the embryo culture medium can provide more accumulation of intracytoplasmic lipid embryos (Mucci et al, 2006), one of the factors that contribute to increased susceptibility of IVP embryos to freezing.

Currently, the most commonly used cryopreservation technique for IVP embryos is vitrification (Dode et al, 2013) because of its simplicity, rapidity and low cost. However, this technique uses high concentrations of cryoprotectants and requires trained personnel and laboratory infrastructure to recover the embryos prior to transplantation (Vajta et al, 1998), limiting its use on site and on a large scale.

On the other hand, the slow freezing of embryos for subsequent direct transfer allows the use of lower concentrations of cryoprotectants, and therefore lower embryo toxicity, despite somewhat higher operating costs (Voelkel and Hu, 1992).

In some embodiments, the present invention provides improved methods of transplanting bovine embryos incubated in serum. Cattle that received fertilized embryos previously incubated in Fetal Bovine Serum (FBS) had similar conception rates as embryos that had not been previously exposed to FBS. In some embodiments, the invention is a method of cryopreserving bovine embryos in the following manner: the recipient cattle have a conception rate similar to that of freshly transplanted embryos. Cattle receiving freshly fertilized embryos have a conception rate similar to that of vitrified embryos and direct transfer/slow frozen embryos. This indicates that the direct transfer/slow freezing method of embryo cryopreservation is as feasible as the vitrification method. For convenience, direct implantation/slow freezing is a suitable alternative to vitrification.

In some embodiments, the oocytes may undergo in vitro maturation prior to fertilization and cryopreservation. In some embodiments, the oocyte is in oxygen (O)₂) Incubation in the presence. In some embodiments, the oocyte is in carbon dioxide (CO)₂) Incubation in the presence. In some embodiments, the oocyte is at 3-9% CO₂Incubation in the presence. In some embodiments, the oocyte is at 5% CO₂In the presence of (a). In some embodiments, the oocyte is at 5% O₂In the presence of (a).

Traditional cattle farming

Animal husbandry is the management and care of farm animals by humans for the benefit where genetic qualities and behaviors that are considered beneficial to humans are further exploited. This term may refer to selectively breeding and raising livestock to promote desirable, practical, athletic, recreational, and research characteristics of the animal.

Animal husbandry combines the art and science of animal husbandry by incorporating long-history practices and modern scientific knowledge into a system that provides animal welfare and provides safe and effective animal management and treatment. As scientists, agricultural specialists and others involved in animals learn new technologies or phase out those that are no longer necessary or appropriate, the practice of animal husbandry will change. Animal husbandry practices range from cow debridement to prevention of damage to herds and farms, to providing habitation for livestock, providing adequate nutrition, and designing breeding strategies.

Techniques such as artificial insemination and embryo transfer have been developed to facilitate breeding. For example, because this technique allows a dam to produce embryos that are not her own, they can be used to ensure that a large number of embryos from a particular high quality dam (or dam strain) can be implanted into a lower quality replacement, thereby expanding the number of offspring that a high quality dam can produce. This approach can greatly increase the number of offspring that a selection of a small number of parent animals of the best quality is likely to produce. However, as discussed herein, such techniques are not typically used for dairy cows. In addition to that, they are often considered too expensive to warrant use in dairy cows. Furthermore, if they tend to broaden a particular genetic trait within a population, genetic diversity within the population will be reduced, increasing the severity of certain disease outbreaks and other risks. The present invention includes, among other things, the insight that this technique, particularly when combined with a crossbreeding strategy, can provide significant advantages in dairy cattle breeding compared to conventional approaches.

Embryo and fertilization techniques

Various techniques have been developed and improved to allow one to control and/or achieve animal breeding optionally without animal sexual intercourse (e.g., natural mating) or even animal contact. Representative such techniques include, for example, in vitro fertilization, artificial insemination, cryopreservation (freezing) of gametes or embryos, induction of multiple ovulations, embryo transfer, sex determination of sperm or embryos, nuclear transfer, cloning, and the like.

In vitro production of ruminant embryos is a three-step process involving oocyte maturation, oocyte fertilization and in vitro incubation. Only 30-40% of such oocytes reach the blastocyst stage, where they can be transplanted into recipients or frozen for future use. The quality of the oocytes can significantly affect the proportion of immature oocytes that form blastocysts, while the post-fertilization incubation environment has a significant impact on blastocyst quality. In some embodiments, the use of sperm of a particular sex in conjunction with in vitro embryo production is a potentially effective means of obtaining offspring of a desired sex. Concerns about the use of semen technology include a significant reduction in fertility of sorted sperm, a lower survival rate of sorted sperm after cryopreservation, and a reduction in the number of sperm that can be separated over a particular period of time. Assessment of embryo quality is a challenge. Morphological assessment is currently the most common method of embryo selection prior to transplantation. Other non-invasive assessment methods include the time to first cleavage division associated with developmental competence. Quantitative detection of gene expression is an additional valuable tool for assessing viability of incubated embryos. There is a great deal of evidence that the incubation conditions to which the embryo is exposed, particularly at the post-fertilization stage, may have interfering effects on the pattern of gene expression in the embryo and may have important long-term consequences.

IVF is a technique for extracting oocytes from donor cows by aspiration from the reproductive system. The selected oocytes are then incubated for a period of 24 hours; this is the so-called mature period. After maturation, the eggs are fertilized after 18 to 22 hours of co-incubation. Embryos remained in medium until day 7, when they were ready for transplantation. This technique has three major advantages over traditional in vivo embryo collection. With IVF, it is not necessary to superovulate cows, nor to synchronize them. This is a significant breakthrough because donor cows are not exposed to hormones that may affect the reproductive health of the animal, and they can work at a time without prior preparation for a procedure. Embryo yields average about 30% of the oocytes harvested, although this number depends on the breed, donor cattle and mating. Another advantage of in vitro fertilization is that animals can be sucked every 20 days instead of every 60 days as in vivo embryo collection. Another benefit of in vitro fertilization is that animals can be harvested in a very small time; this will have a major impact on breeding selection as it reduces the generation interval of animals with a particular desirable trait.

Artificial Insemination (AI) has been used to obtain offspring over 200 years from genetically superior males. The well-known methods of cryopreservation (freezing) and storage of semen have enabled more livestock producers to use AI. Like cryopreservation of semen, embryo freezing can lead to global commercialization of animals with high genetic quality. Semen from bulls is particularly suitable for freezing and long-term storage. In the dairy industry where a large number of cows are intensively managed, artificial insemination is simple, economical and successful. Artificial insemination breeds more than 60% of cows in the united states. However, the situation with beef cattle is different, and generally the feedlot is usually kept in pasture or pasture conditions. In the beef industry in the united states, artificial insemination accounts for less than 5% of insemination.

The development of ET technology allows producers to obtain multiple offspring from genetically superior females. Fertilized embryos can be recovered from females (also called embryo donors) of superior genetic value by surgical or non-surgical techniques. Genetically superior embryos are then transferred to less genetically valuable females (also referred to as embryo recipients). In the case of cattle, an effective technique would allow recovery of fertilized embryos without surgery, but only one or sometimes two embryos are produced per normal reproductive cycle. To increase the number of embryos that can be recovered from genetically superior females, embryo donors are treated with hormonal regimens to induce multiple or superovulation.

The beef industry in the united states prefers male calves, which tend to have higher body weight and higher feed efficiency (compared to female or young cows) when placed in feedlots for the growth and finishing stages of meat production. In contrast, the dairy industry prefers young cows, which eventually produce edible offspring and milk. Thus, there is a need for a method of determining the sex of sperm or embryos so that a producer can control the sex of their livestock offspring.

Since the mid-80's of the 20 th century, the transfer of nuclei taken from early cells (possibly undifferentiated blastomeres) or somatic cells (fibroblasts, skin, heart, nerves or other body cells) blastomeres into enucleated oocytes (unfertilized female oocytes, with nuclear removal) has been developed. Such "nuclear transfer" produces multiple copies of animals that are themselves nearly identical to other animals (transgenic animals, genetically superior animals or animals that produce large amounts of milk or have other desirable characteristics, etc.). This process is also known as cloning. Somatic cell nuclear transfer has been used to date for cloning cattle, sheep, pigs, goats, horses, mules, cats, rabbits, rats and mice.

This technique involves incubating somatic cells from appropriate tissues (fibroblasts) of the animal to be cloned. Nuclei from the incubated somatic cells are then microinjected into enucleated oocytes obtained from another individual of the same or closely related species. By a process not yet understood, somatic cell-derived nuclei are reprogrammed to gene expression patterns suitable for directing the normal development of embryos. After further incubation and development in vitro, the embryos are transferred to recipient females with the end result that live offspring are born. The success rate of animal breeding by nuclear transfer is typically less than 10% depending on a number of factors including species, source of recipient eggs, cell type of donor nuclei, handling of donor cells prior to nuclear transfer, and the technique used for nuclear transfer.

The present disclosure shows the effectiveness of improved cryopreservation techniques for freezing and thawing ungulate embryos. The present invention demonstrates that such techniques can provide significant benefits to the dairy industry.

In some embodiments, the stored embryos may be supplied to other farms and businesses, for example, enabling them to produce hybrid progeny and/or hybrid populations. In some embodiments, the present invention allows for a commercial method of screening hybrid cattle and reconstituting high-potency hybrid cattle by selective breeding using the F0 gamete of its parent.

Antifreezing agent

As described herein, the present invention provides techniques for cryopreservation of bovine embryos and/or for achieving fertilization using cryopreserved bovine embryos. In some embodiments, the cryoprotectant used according to the invention is or comprises an intracellular cryoprotectant. In some embodiments, the cryoprotectant used according to the invention is or comprises an extracellular cryoprotectant. In some embodiments, exemplary cryoprotectants (e.g., for use as intracellular cryoprotectants) may be or include: dimethyl sulfoxide (DMSO), glycerol, polyethylene glycol (PEG), and combinations thereof. In some embodiments, an exemplary cryoprotectant (e.g., for use as an extracellular cryoprotectant) may be or comprise: sucrose, trehalose, dextrose, and combinations thereof. In some specific embodiments, the cryoprotectant used in accordance with the present invention may be or comprise propylene glycol.

Stage of embryonic development

In some embodiments, embryos may be cryopreserved at various stages of development. In some embodiments, the embryo may be cryopreserved at a developmental stage selected from the group consisting of morula, early blastocyst, and expanded blastocyst. After the blastocyst is formed, the embryo is ready for implantation into the uterine wall. In some embodiments, the early blastocyst stage is characterized by the cavity just beginning to form and blastocyst cells that are not yet distinguishable. In some embodiments, the expanded blastocyst stage is characterized by a fully formed cavity.

Freezing preservation device

The present invention provides devices for cryopreservation of embryos. In some embodiments, the device comprises cryopreserved embryos in a cryopreservation solution located within a first region within the device, the first region flanked by: a second region and a third region, each region comprising an air composition, the second region and the third region flanking: a fourth zone and a fifth zone, each zone containing a thawing solution, the fourth and fifth zones flanked by: a sixth zone and a seventh zone, each zone containing air, the sixth and seventh zones being flanked by: an eighth zone and a ninth zone, each zone containing a thawing solution. In some embodiments, one or more regions of the device are chambers.

In some embodiments, the present invention provides a plurality of devices for freezing embryos. In some embodiments, each of the plurality of devices contains embryos from a single mating.

In some embodiments, the invention provides methods comprising the step of preparing a plurality of embryos; cryopreserving a plurality of embryos; and the embryos were transplanted at a conception rate of about 40%. In some embodiments, the embryos are optionally stored for a period of time between cryopreservation and transfer to a recipient cow. In some embodiments, the time period between cryopreservation and transplantation into a recipient cow can be minutes, hours, days, weeks, months, years, or longer (e.g., multiples thereof). In some embodiments, the embryos are stored for a period of time of less than about 40 years, about 35 years, about 30 years, about 25 years, about 20 years, about 15 years, about 10 years, about 9 years, about 8 years, about 7 years, about 6 years, about 5 years, about 4 years, about 3 years, about 2 years, or about 1 year. In some embodiments, embryos are stored for a period of time less than about 12, about 11, about 10, about 9, about 8, about 7, about 6, about 5, about 4, about 3, about 2, about 1 month or less. In some embodiments, embryos are stored for a period of time of less than about 6 weeks, about 5 weeks, about 4 weeks, about 3 weeks, about 2 weeks, about 1 week, or less. In some embodiments, the embryos are stored for a period of time of less than about 7 days, about 6 days, about 5 days, about 4 days, about 3 days, about 2 days, or about 1 day. In some embodiments, the embryo is stored for a period of time less than about 24 hours, about 20 hours, about 16 hours, about 12 hours, about 8 hours, about 4 hours, about 3 hours, about 2 hours, or about 1 hour. In some embodiments, the embryo is stored for a time period of less than about 60 minutes, about 50 minutes, about 40 minutes, about 30 minutes, about 20 minutes, about 10 minutes, about 5 minutes, about 4 minutes, about 3 minutes, about 2 minutes, or about 1 minute.

In some embodiments, the embryo may be stored for minutes, days, or years prior to transfer to the recipient cow. In some embodiments, the period of time that an embryo may be stored may be minutes, hours, days, weeks, months, years, or longer (e.g., multiples thereof). In some embodiments, the embryos are stored for a period of time of less than about 40 years, about 35 years, about 30 years, about 25 years, about 20 years, about 15 years, about 10 years, about 9 years, about 8 years, about 7 years, about 6 years, about 5 years, about 4 years, about 3 years, about 2 years, or about 1 year. In some embodiments, embryos are stored for a period of time less than about 12, about 11, about 10, about 9, about 8, about 7, about 6, about 5, about 4, about 3, about 2, about 1 month or less. In some embodiments, embryos are stored for a period of time of less than about 6 weeks, about 5 weeks, about 4 weeks, about 3 weeks, about 2 weeks, about 1 week, or less. In some embodiments, the embryos are stored for a period of time of less than about 7 days, about 6 days, about 5 days, about 4 days, about 3 days, about 2 days, or about 1 day. In some embodiments, the embryos are stored for a period of time less than a period of about 24 hours, about 20 hours, about 16 hours, about 12 hours, about 8 hours, about 4 hours, about 3 hours, about 2 hours, or about 1 hour. In some embodiments, the embryo is stored for a time period of less than about 60 minutes, about 50 minutes, about 40 minutes, about 30 minutes, about 20 minutes, about 10 minutes, about 5 minutes, about 4 minutes, about 3 minutes, about 2 minutes, or about 1 minute.

In some embodiments, the step of cryopreserving comprises performing in a device. Embryos can be cryopreserved within the device according to the methods disclosed herein. In some embodiments, the step of cryopreserving comprises cryopreserving a plurality of embryos, each in its own device, thereby creating a set of devices. In some embodiments, a plurality of devices are maintained for a first period of time. In some embodiments, after the first period of time, at least one embryo is transferred to a recipient cow; and optionally holding the remaining embryos for a second period of time. In some embodiments, the second time period may be up to 40 years. In some embodiments, embryos may be stored for minutes, days, or days prior to transfer to a recipient cow. In some embodiments, the second period of time over which embryos may be stored may be minutes, hours, days, weeks, months, years, or longer (e.g., multiples thereof). In some embodiments, the embryos are stored for a period of time of less than about 40 years, about 35 years, about 30 years, about 25 years, about 20 years, about 15 years, about 10 years, about 9 years, about 8 years, about 7 years, about 6 years, about 5 years, about 4 years, about 3 years, about 2 years, or about 1 year. In some embodiments, embryos are stored for a period of time less than about 12, about 11, about 10, about 9, about 8, about 7, about 6, about 5, about 4, about 3, about 2, about 1 month or less. In some embodiments, embryos are stored for a period of time of less than about 6 weeks, about 5 weeks, about 4 weeks, about 3 weeks, about 2 weeks, about 1 week, or less. In some embodiments, the embryos are stored for a period of time of less than about 7 days, about 6 days, about 5 days, about 4 days, about 3 days, about 2 days, or about 1 day. In some embodiments, the embryos are stored for a period of time less than a period of about 24 hours, about 20 hours, about 16 hours, about 12 hours, about 8 hours, about 4 hours, about 3 hours, about 2 hours, or about 1 hour. In some embodiments, the embryo is stored for a time period of less than about 60 minutes, about 50 minutes, about 40 minutes, about 30 minutes, about 20 minutes, about 10 minutes, about 5 minutes, about 4 minutes, about 3 minutes, about 2 minutes, or about 1 minute.

In some embodiments, the device comprises a container for holding one or more cryopreserved embryos. In some embodiments, the container includes a region or chamber for holding embryos in solution flanked by bubbles. In some embodiments, the container comprises a region or chamber for separating embryos from other embryos. In some embodiments, the container comprises a straw.

Examples of the invention

The objective of this study was to compare the pregnancy rates obtained after direct transplantation of fresh, vitrified or frozen ETIVP bovine embryos. Oocytes recovered by egg collection Girolando female (n 3171) were selected at 38.5 ℃ with 5% CO₂And saturated humidity, IVM was performed for 24 hours. In vitro fertilization was performed with 5 Holstein bulls thawed, sex-controlled semen. After in vitro fertilization, 5% CO at the same temperature and humidity for IVM and IVF₂And 5% of O₂The hypothetical zygotes were denuded and incubated for 7 days. Stage I embryos of BL or BX were transferred to fresh, vitrified or frozen for Direct Transfer (DT). The embryo is transferred to a previously synchronized recipient. The fertilization rate of the fresh embryo is 51.35% (133/259), the fertilization rate of the vitrified embryo is 34.62% (84/234), and the fertilization rate of the directly transferred embryo is 42.11% (96/228). p is a radical of<A probability level of 0.05 was considered significant. The fertilization rates obtained from vitrification and direct transfer of IVP embryos suggest that cryopreservation of IVP embryos yields similar results to those obtained after transfer of fresh IVP embryos. Highlighting the potential for cryopreservation of IVP embryos and the positive aspects of direct transfer convenience.

Example 1: materials and methods

All reagents were purchased from Sigma (st. louis, MO, USA) unless otherwise indicated. Examples 4 and 5 used the follicular aspiration procedure, in vitro maturation and in vitro fertilization described in examples 1-3.

Example 2: collection and bulk of oocytesExo-maturation

This was done by performing 112 ova aspiration (OPU) under ultrasound guidance in blood from 36 female donors 1/2 hybridized with Holstein at Gir. After aspiration, the oocytes (n 3171) were used

Hepes buffered TCM-199 medium (GIBCOBRL, GrandIsland, NY) supplemented with 10% Fetal Bovine Serum (FBS) (GIBCOBRL, GrandIsland, NY), 0.20mM sodium pyruvate, and 83.4mg/mL amikacin (BIOCHIMICO institute, Riode Janeiro, Brazil). Oocytes were pre-selected and sorted into mobile laboratories set up on farms. After selection of oocytes, they were transferred to BDfalcon5mL polystyrene tubes containing 400. mu.L of 1mg/mLFSH (Folltropin) supplemented with 10% FBS^TMBioniche animal health, Belleville, Canada), 350. mu.L of mineral oil-covered 50mg/mLhCG (Profasi)^TM，Serono，

Brazil) and estradiol (1mg/mL), sodium pyruvate 0.20mm, and 83.4mg/mL amikacin in TCM-199 medium. The thawed oocytes were transported to a laboratory in MogiMirim/SP and stored in the same transport tube with maturation medium for 24 hours from the moment of OPU.

Example 3: semen preparation and In Vitro Fertilization (IVF)

IVF was performed using Holstein bull (n ═ 5) female semen. The semen was thawed (35 ℃, 30 seconds) and washed twice by centrifugation (6000rpm, 5min) in 1mL of alp supplemented with 0.2mM pyruvate and 83.4g/mL amikacin, buffered with 10mM hepes. Semen concentration is adjusted to 2 × 10⁶Sperm (sptz) mobile/mL. Under mineral oil, 10 microliters (10 μ M) of 50 μ L LAPP-FIV (TALP supplemented with 10 μ g/mL heparin, 18 μ M penicillamine, 10 μ M, and 8 μ M hipotaurina epinephrine) were added to each drop⁵sptz). Subsequently, 25-30 oocytes were added dropwise at a time. Incubators at 38.5 ℃ with 5% CO²And maximum humidity in air for 20-24 hours.

Example 4: experiment I- -Presence or absence of Fetal Bovine Serum (FBS)Fresh IVP embryos transferred after incubation in the Presence

In vitro Incubated (IVC) embryos

Oocytes (n ═ 665) were collected from Girolando donors (n ═ 25) by follicular aspiration under ultrasound guidance. These oocytes were fertilized in vitro with sex-controlled semen from the same Holstein bull, and occasionally distributed between groups.

Group using FBS-putative fertilized eggs (n 303) were incubated in 100 μ LSOF (synthetic oviduct fluid) supplemented with 2.5% FBS + 0.5% Bovine Serum Albumin (BSA) under mineral oil (Wells et al, 1999). On the third day (D3) and fifth day (D5) of IVC, 50% of the drop volume was replaced with new medium ("feed"). Media incubated with the same media was "fed" during early embryo development.

The group without FBS-putative zygotes were incubated under mineral oil in 100 μ SOF supplemented with 0.5% Bovine Serum Albumin (BSA) +10 μ MEDTA without FBS (n-362). On the third day (D3) and fifth day (D5) of IVC, 50% of the drop volume was replaced with new medium ("feed"). Incubation media "fed" with the same media were used in early embryo development.

After 7 days of incubation, embryos of the groups with (n-82) or without FBS (n-88) were transferred to previously synchronized recipient cattle. The first third of females in lactation serve as recipients. To synchronize the receptors, the following protocol was used:

day 0 (D0) -2mg estradiol benzoate

+ intravaginal implant placement

Seventh day (D7) -5mL prostaglandin F2 a

-ninth day (D9) removal of implant and applicationAdding 1mg estradiol cypionate

Eighteenth day (D18) embryo transfer

In experiment 1, conception rates were compared in embryos incubated in two different media, supplemented or not with FBS. As can be seen from table 1, there is no difference between the two groups. This example shows that fresh embryos grown in FBS supplemented medium have similar viability and conception rates as embryos not grown in FBS.

TABLE 1 conception rates of fresh embryos grown with or without FBS.

^ap<0.05

Example 5: comparison of conception rates of fresh, vitrified or cryo-transferred IVP embryos for direct transplantation

In vitro Incubated (IVC) embryos

Hypothetical zygotes were CO-incubated with granulosa cells (occasional groups of 25 oocytes per drop) in an incubator (38.5 ℃ with 5% CO2 and maximum humidity in air) following the procedure described in examples 2 and 3. Fresh or vitrifted embryos were incubated in 100 μ LSOF (Wells et al, 1999) supplemented with 2.5% FBS + 0.5% Bovine Serum Albumin (BSA) under mineral oil. On the third day (D3) and fifth day (D5) of IVC, 50% of the drop volume was replaced with new medium ("feed"). The medium "fed" is the same medium used in early embryo development. Cleavage rate was assessed on the third day of incubation (D3).

Embryos frozen for direct transfer were incubated in 100 μ L of FBS-free modified SOF drops and supplemented with 0.5% Bovine Serum Albumin (BSA) + EDTA10 μ M under mineral oil only. On the third day (D3) and fifth day (D5) of IVC, 50% of the drop volume was replaced with new medium ("feed"). The medium "fed" is the same medium used in early embryo development. Cleavage rate was assessed on the third day of incubation (D3).

At the end of the incubation period (D7), expanded blastocysts classified as grade 1 were loaded and transplanted into fresh, previously synchronized recipients. In the absence of all receptors producing embryos, the remaining embryos were vitrified according to the protocol described by SANCHES et al. (2013) or frozen for later direct transplantation.

Embryo vitrification

In this work, embryo cryopreservation was used for vitrification methods according to the protocol previously described by SANCHES et al, 2013.

Briefly, embryos (Bx, n 234) were exposed to equilibration solution (SE 10% EG) + 10% dimethyl sulfoxide (DMSO) for 1 minute and then to vitrification solution (VS 20% EG + 20% DMSO) for 20 seconds. The embryos were mounted during 20 seconds of exposure to the vitrification liquid

(Kitazato-Shizuoka-Japan), 3 to 5 embryos per Cryotop and immediately placed in liquid nitrogen. Embryo vitrification is based on the technique Cryotop described by KUWAYAMA et al (2005). This method uses the concept of minimal volume, where the embryos are placed in a very thin plastic film that is attached to a plastic rod for convenient handling. The vitrification solutions used were prepared in four-well plates (NUNCS/A, Roskilde, Denmark). TCM-HEPES medium (TCM-199+25mM HEPES + 10% FBS) is the basis for the preparation of solutions containing EG and DMSO, and is added only at the time of use. In both groups, the Equilibrium Solution (ES) was supplemented with 20% FBS and the Vitrification Solution (VS) was supplemented with 0.5M sucrose. First, embryos are placed on holding medium (TCM-HEPES) where they are removed (3-5 at a time) and into wells 1 containing ES. In this solution, embryos were retained for one minute and soon later transferred to wells 2 containing VS, exposed for 20 seconds. Therefore, the embryos are immediately aspirated and placed on a plastic film at the Cryotop tip, and the samples are immersed in liquid nitrogen.

Lysis of vitrified embryosJelly made from plant

To thaw the vitrified embryos, Cryotops containing the embryos were exposed to air for 4 seconds and then soaked in a heated solution (TCM-Hepes + sucrose 0.3 molar) at a temperature of approximately 35 ℃. The vitrification solution was removed by two exposures (5 minutes each) with a gradient of 0.3M sucrose and 0.15 sucrose, respectively, before being transferred to the maintenance medium TCM-Hepes (Vieira et al 2002; Mezzalira et al 2004).

Slow thawing of embryos

In general, embryos (n ═ 228) were cryopreserved by the slow freezing method previously described for embryos obtained in vivo (volelkel and Hu, 1992). Exposing the blastocysts and expanded blastocysts to a freezing solution consisting of 1.5M ethylene glycol

For 10 minutes. The incubation dish containing SC and embryos was kept on the heated incubation plate up to 35 ℃ during this period. Loading the embryos into a 0.25ml pipette, placing the embryos on a central column consisting of 1.5M ethylene glycol solution, thawing the solution from four columns

Surrounding and interspersed with air columns (fig. 1). The thawing Solution (SD) consisted of 0.75MEG, EG1.5M in DPBS (Nutricell-Campinas-Brazil) at a ratio of 1: dilution at a ratio of 1. After loading, embryos are placed in a freezer previously stabilized at-6 ℃ (II)

-Uberaba-Brazil). Two minutes after placement in the machine, crystallization ("seeding") was performed immediately above and below the embryonic column. Embryos were kept at-6 ℃ for 10 min.

The freezing curve was started and the temperature was lowered by 0.5 ℃ per minute until a level of-32 ℃ was reached. At the end of the freezing curve, the embryos are immersed directly in liquid nitrogen, where they are stored before being transplanted into recipients. See also the overview of fig. 2A.

Thawing and direct transplantation

In the case of transferring cryopreserved embryos for direct transfer, the embryos are removed from a liquid nitrogen container, exposed to air at room temperature for 10 seconds, and then immersed in hot water at 35 ℃ for 30 seconds. The pipette was dried with paper towel and gently stirred until the inner 5 columns were mixed. The goal was to mix 4 columns of thawed solution with a column of frozen solution so that rehydration had begun within the pipette. After mixing the columns, the embryos are transferred to the uterine horns of the recipients. See generally fig. 2B.

Females used as recipients of fresh embryos, vitrification, or direct transfer are in the first third of the lactation period. The synchronization scheme was the same as in example 4.

Statistical analysis

As a fixed effect are synchronized protocol variables, recipient age, animal class (lactation or dry) and bull for in vitro fertilization. Conception rates for 30 and 60 days were analyzed by binomial Logistic regression of IBMSPSSSstatics version 22 (IBM Inc., Armonk, NY). Probability level p <0.05 was considered significant.

Results

In example 5, conception rates at 30 and 60 days of fresh embryo transfer, vitrification or freezing direct transfer were compared (table 2). In this case, the fresh embryo transfer 51.35% (133/259) was different from the two groups using cryopreservation. However, there was no difference in conception rates of vitrified embryos (p <0.05) 34.62% (84/234) compared to directly transferred embryos 42.11% (96/228).

Table 2: comparison of embryo conception rates between 30 and 60 days for fresh, vitrified or frozen directly transferred IVP embryos with the loss rates of group 3 embryos at the same time.

^a,bp<0.05

Discussion of the related Art

Detailed are comparisons of conception rates of IVP embryos transplanted in fresh, vitrified or frozen direct transplants. This is the first such study, particularly for the consistent number of embryos transferred in a tumor-bovine general.

2013 data provided by Perry (2014) show that only 8.9% of transplanted IVP embryos are cryopreserved worldwide. Without wishing to be bound by any particular theory, we suggest that this low rate may be due to the higher sensitivity and/or lower viability of these cryopreserved embryos compared to fresh frozen embryos (e.g., when exposed to embryo resuscitation and/or transplantation techniques); this low ratio is a limiting aspect of most commercial laboratories using this technology (George, 2008). However, in view of the increasing number of IVP embryo production, finding an appropriate strategy for freezing embryos in vitro has become crucial.

When considering genetic material, supplies, materials and processes, the world deals with more than 90% of embryos produced in vitro (Perry, 2014), which reflects more extensive losses. Furthermore, when it is desired to work with only fresh embryos, the logistics of managing the embryos implanted in the recipient become even more important. All of these disadvantages, the disposal of the remaining embryos increases the cost of the technology, making it less profitable and competitive. From the point of view of PONTES (2013), brazil corporation rejected approximately 25,000 IVP embryos between 2002 and 2008 because there was no complete cryopreservation protocol.

In addition to the challenges associated with cryopreservation and/or the use of cryopreserved embryos, there is a considerable gap in the technology available for bovine animals of different ethnic groups. It is understood that there are various reproductive differences between common and tumor bovine animals. For example, one difference is the characteristics of the organelles. VISINTIN et al (2002) work with in vivo embryos and demonstrate specific characteristics between tumor and common bovine embryos, particularly the amount of intracytoplasmic lipids. Considering the climatic and geographical conditions in brazil, the goal of this work was to use embryos derived from the buffalo-buffalo herd, including the donor Girolando. This cross entails 80% milk production in brazil due to the good adaptability and low cost of milk production on pastures (Girolando, 2015).

Interest in Girolando female embryo production has provided several publications in recent years. PONTES et al (2010) compared the embryo yields at the stage of Holstein, Gir and Gir donor follicles. In this study we observed high embryo/aspiration yields (3.2 and 2.2, respectively) for Gir cows, Holstein cows. However, Girolando has an average two-fold higher embryo yield (5.5 blastocysts) compared to the other two varieties. The present invention recognizes that this superior performance in IVP bovine cheilous embryos allows for the development of improved embryo cryopreservation techniques, e.g., based on sample abundance in feasibility experiments and obtaining pregnancy.

IVP embryos have lower freezing tolerance compared to in vivo embryos (Abe et al, 2002), and the reason for this increased sensitivity is mainly due to higher accumulation of intracellular lipids found in the cytoplasm of IVP embryos (Abe et al, 2002; Rizos et al, 2002; Sudano et al, 2011). In this case, Fetal Bovine Serum (FBS), which is a supplement to the medium used in the culture, was identified as responsible for the lower embryo survival after freezing (Diez et al, 2001; Abe et al, 2002; Lonergan et al, 2003). However, the highest concentration of intracytoplasmic lipid droplets cannot be considered the only detrimental factor for cryopreservation, one of the problems is multifactorial, involving strict quality control at various stages of IVP, with the view of cryopreservation to obtain embryo quality (Sudano et al, 2013)

In example 4, follicular aspiration was performed in the same group of donors and embryos were incubated in the absence or presence of FBS. The objective was to compare the pregnancy rates (with or without FBS) of two groups of fresh embryos transferred. There are some reports (George et al, 2008) that embryos incubated with fcs (fetalcalfserum) have higher elongation of embryos and placenta compared to IVP embryos incubated with BSA.

A direct comparison between these works is valuable, for example, because most other works only evaluate the rate of re-expansion and hatching of embryos, and do not extend to transplantation of produced embryos. In addition, in each of these studies, there were many differences between the composition of the medium and the incubation conditions.

In the study described in example 4, no pregnancy differences were observed between groups (P <0.05), which allowed us to conclude that dispensing FBS for in vitro incubation led to several pregnancies consistent with not using FBS.

The present invention recognizes that in addition to considering FBS and incubation conditions, there is another important aspect to consider: an anti-freezing agent. Cryopreservation protocols should be able to prevent the formation of intracellular ice crystals and attempt to minimize toxicity and osmotic stress on cells during freezing (Campos-Chillon et al, 2006). Thus, many cryoprotectants such as glycerol and Ethylene Glycol (EG) are toxic to embryos (Dochi et al, 1988). Reducing the time that embryos are exposed to these cryoprotectants before and after freezing can reduce toxic effects, resulting in higher embryo viability after thawing (Sommerfield and Niemann, 1999).

In the early 90's of the 20 th century, Voelkel and Hu (1992) demonstrated that the use of ethylene glycol as a cryoprotectant can replace direct transfer of freeze-thawed embryos with a somewhat lower conception rate than that obtained with fresh embryos (VoelkelHu, 1992, Leibo and Mapletoft, 1998). The direct transfer method allows the rehydration step in thawed embryonic cells to be simplified, making them more readily available, and allows for a simple technique to be performed in the field. Since then, direct transfer has been widely accepted for freezing of in vivo-produced embryos for collection of superovulated donors.

However, for IVP embryos, the most widely used method for freezing IVP embryos is vitrification (morato os and Mogas, 2014), mainly due to the speed of freezing and the low cost. This makes embryo transfer a more efficient technique, no longer dependent on the availability of synchronous recipients. Whether frozen, vitrified or directly transplanted, the conception rate is lower than that of fresh embryos (Leibo and mapeltoft, 1998). The drawback of vitrification is the need for a qualified embryologist to reheat the embryos, which is beyond the minimum structure required in the laboratory-further complicating their use on site and on a large scale (Morat Lo and Mogas, 2014).

In this study, we used a protocol for slow freezing (direct transfer) of embryos using 1.5M ethylene glycol as an embryo cryoprotectant. However, in experiments performed before our team, we found that when embryos were frozen in a central column of 1.5M ethylene glycol, the side column consisting of only DPBS, the embryo hatchability after thawing was lower. Without wishing to be bound by any particular theory, we suggest that one explanation for our observations is that embryos rehydrate very quickly when in direct contact with post-thaw DPBS.

We chose to examine the use of a thawing solution consisting of 0.75M ethylene glycol arranged in four columns on either side of the embryo. In this way, the flow into the embryonic cells can occur more slowly, maintaining their integrity. A similar strategy was proposed to freeze embryos in vivo, using a side column towards the embryo, consisting of a solution called "holding medium" consisting of 0.37 moles of ethylene glycol (Voekel and Hu, 1992). In this work, the conception rate of the experimental group was the same as that of the control group (50%). Although the conception rate is relatively low, about 40%, it is important to take into account the lower pressure support of the in vivo embryo on its development and to provide a higher pregnancy rate. Therefore, the in vitro generated package strategy of Oncomeus-Bos taurus embryos can be considered successful.

Another important insight observed in this study is that embryos have the lowest survival rate when they are frozen from cryopreserved IVP embryos at the compact morula stage, compared to embryos classified as blastocysts and enlarged blastocysts. The authors examined the hatchability of morula and blastocyst to find similar results as an indicator of embryo viability after cryopreservation by the slow method (polradand leibo, 1993), but there was no consensus on the optimal stage of embryo cryopreservation (Saragusty and Arav, 2011).

The conception rate was higher at 30 days of IVP fresh embryo transfer (51.4%) compared to that obtained by vitrification (34.6%) and direct transfer (40.19%) of cryopreserved IVP embryos (P > 0.05%). These results are higher than those obtained by LIM et al (2008). IVP embryos incubated under serum-free conditions were also preserved by slow freezing (22.9%) more than IVP embryos preserved by vitrification freezing using open tube drawing technique (Vajta et al, 1998).

Without wishing to be bound by any particular theory, we propose that the combination of FBS-free incubation plus loading strategy to place embryos in a pipette device may be the reason for the success of our protocol. The conception rate at 60 days of gestation was also assessed, with higher (43.2%) fresh embryos transplanted (P >0.05), comparable results to those published by Hasler et al (1995), who had obtained IVPtaurus 42% of the designed conception rate at 7 days post-fertilization.

The findings herein demonstrate the superiority of certain direct implantation (e.g., slow freezing) methods compared to vitrification performed herein. In some embodiments of the invention, it may be desirable to manufacture a set of embryos (e.g., using direct transfer/slow freezing techniques), for example, which may be held in a first location (e.g., a production location). In some embodiments, the transfer of these retained embryos may be more practical than using vitrification techniques.

In some embodiments, the techniques described herein utilize gender separated semen; IVP is generally considered to be a method that allows the most efficient use of sex separated semen, and is particularly valuable in dairy farming.

In some embodiments, one or more changes or improvements may be employed, for example, to reduce the rate of early embryo loss observed in certain studies described herein (e.g., when comparing 30-day and 60-day pregnancies).

In addition, the present invention provides the achievement and advancement of pregnancy through cryopreservation of IVP embryos. We conclude that: in vitro produced tumourous-bovine embryos can provide about 40% pregnancy rates after cryopreservation by vitrification methods or slow freezing/direct transplantation. One of ordinary skill in the art reading this disclosure will appreciate that application of its teachings to different contexts (e.g., different varieties, different species, different subspecies, different crosses, and/or different hybrids, etc.) would reasonably be expected to achieve at least about 10%, about 11%, about 12%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, or about 50%, in each case well above the pregnancy rates typically observed using the prior art techniques (e.g., about 9%).

Of particular note, the techniques described herein represent an important step in the in vitro production of embryos by specifically improving and or initiating (e.g., by allowing for a conception rate of at least 30%) an effective slow freezing/direct transfer strategy, becoming a widely used biotechnology in animal husbandry.

Identity of

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. The scope of the invention is not limited by the above description but is as set forth in the following claims.

Claims

1. An apparatus for cryopreservation of embryos, the apparatus comprising:

a container;

frozen embryos in a freezing solution comprising between 1 and 4 moles of ethylene glycol located within a first region of the container flanked by:

a second zone and a third zone, each zone containing air, the second zone and the third zone being flanked by:

a fourth zone and a fifth zone, each containing a thawing solution comprising 0.75M ethylene glycol in Dulbecco's phosphoric acid buffer solution, the fourth and fifth zones flanked by:

a sixth zone and a seventh zone, each zone containing air, the sixth zone and the seventh zone being flanked by:

an eighth zone and a ninth zone, each containing a thawing solution comprising 0.75M ethylene glycol in Dulbecco's phosphoric acid buffer solution.

2. The device for cryopreservation of embryos of claim 1, wherein the freezing solution comprises 0.2 to 1.3M ethylene glycol.

3. The device for cryopreservation of embryos of claim 1, wherein the freezing solution comprises 1.5 moles of ethylene glycol.